pygeoapi is a Python server implementation of the OGC API suite of standards. From version 0.23.0 to before version 0.23.3, a raw string path concatenation vulnerability in pygeoapi's STAC FileSystemProvider plugin can allow for requests to STAC collection based collections to expose directories without authentication. The issue manifests when pygeoapi is deployed without a proxy or web front end that would normalize URLs with .. values, along with a resource of type stac-collection defined in configuration. This issue has been patched in version 0.23.3.